Former FBI director James Comey pleaded not guilty to charges of making false statements to Congress and obstructing a congressional proceeding / AFP

A federal judge on Monday dismissed the criminal cases against former FBI director James Comey and New York Attorney General Letitia James, dealing a blow to US President Donald Trump's efforts to prosecute his political opponents.

District Judge Cameron Currie threw out both cases on the grounds that the US attorney handpicked by Trump who brought the charges was unlawfully appointed.

Comey, 64, was charged in September with making false statements to Congress and obstructing a congressional proceeding in what was widely seen as retribution by the Republican president against a political opponent.

James, 67, a Democrat who successfully prosecuted Trump for fraud, was indicted the following month on one count of bank fraud and a second one of making false statements to a financial institution.

Both indictments were brought by interim US Attorney Lindsey Halligan, who was described by Currie in her dismissal rulings as "a former White House aide with no prior prosecutorial experience."

Top federal prosecutors are subject to Senate confirmation and Currie said Halligan had been unlawfully appointed because her predecessor was also serving in acting capacity and US law does not allow two successive interim prosecutors.

"All actions flowing from Ms Halligan's defective appointment, including securing and signing Mr Comey's indictment, were unlawful exercises of executive power," the judge said.

"And because Ms Halligan had no lawful authority to present the indictment, I will grant Mr Comey's motion and dismiss the indictment without prejudice."

She made a similar ruling in James's case.

The indictments of Comey and James came after the interim US attorney for the Eastern District of Virginia, Erik Siebert, stepped down after reportedly telling Justice Department leaders there was insufficient evidence to charge them.

Attorney General Pam Bondi replaced Siebert with Halligan, and she secured the indictments in Virginia.

Dismissing the indictments without prejudice leaves open the possibility of the charges being filed again, although the statute of limitations in the Comey case may have since expired.

Comey and James also sought to have the indictments dismissed on the grounds they were a vindictive prosecution. Those arguments were heard by a different judge.

- 'Baseless charges' -

Comey, in a post on Instagram, welcomed the dismissal of a case that he said was "based on malevolence and incompetence."

"This case mattered to me personally, obviously, but it matters most because a message has to be sent that the president of the United States cannot use the Department of Justice to target his political enemies," he said.

Comey urged Americans to "stand up and show the fools who would frighten us, who would divide us, that we're made of stronger stuff, that we believe in the rule of law."

James also welcomed the dismissal of the indictment and said she will "remain fearless in the face of these baseless charges."

After Trump left the White House in 2021, James won a civil fraud case against him, alleging he and his real estate company had unlawfully inflated his wealth and manipulated the value of properties to obtain favorable bank loans or insurance terms.

Comey was appointed to head the FBI by president Barack Obama in 2013 and was fired by Trump in 2017 amid a probe into whether any members of the Trump presidential campaign had colluded with Moscow to sway the 2016 vote.

The charges against Comey came just days after Trump publicly urged Bondi to take action against the former FBI director and others he sees as enemies -- a stunning departure from the principle that the Justice Department must be free from White House pressure.

Since taking office in January, Trump has taken a number of punitive measures against perceived enemies, purging government officials he deemed to be disloyal, targeting law firms involved in past cases against him and pulling federal funding from universities.

Another Trump critic, his former national security advisor John Bolton, has been indicted on 18 counts of transmitting and retaining classified information.

In another development, the Pentagon said Monday that it was considering a court-martial against Democratic senator and former astronaut Mark Kelly for appearing in a video urging troops to refuse unlawful orders.

cl/dw